This invention generally relates to aircraft radar countermeasures and more particularly to an aircraft-launched, self-inflated, low drag aerodynamic decoy which provides a large radar reflection and doppler frequency return at millimeter wave frequencies to defeat ground-based enemy radar and radar-guided weapons.
The use of chaff to defeat the radar function by denying it range and direction (azimuth and elevation) information is a well-known and practiced technique in the art of radar jamming. Conventionally, passive chaff elements in the form of discrete dipoles are dispensed by an aircraft to form a cloud which creates a credible false target to ground-based radar. The dipoles are comprised of low mass slivers of metallized mylar, glass or other suitable dielectric material and these are ejected by the aircraft into its adjacent windstream where vehicle-induced turbulence or wind shear effects are available for dispersion and cloud formation.
One of the problems with chaff of the type described is that current practices are limited to frequencies below 20 GHZ and furthermore, upon ejection, they rapidly slow down and fall at an almost constant rate due to their very low mass. Accordingly, the useful life of the chaff is very short for lack of a doppler frequency return to the enemy radar. The radar can therefore update its return information and easily determine the location of the aircraft because of its doppler frequency signature.
A primary purpose of this invention is to provide a radar decoy which matches the doppler spectra so that doppler-sensitive threat systems cannot detect a difference between the decoy and the aircraft being protected. Further, the decoy provides an extended operational life for greater aircraft protection.